Cationic antibacterial compounds are known.
U.S. Pat. No. 4,370,314 discloses antibacterial quaternary ammonium compounds in which one of two of the substituents on the quaternary nitrogen has a chain length of 8 to 20 carbon atoms. The remaining substituents have a lower number of carbon atoms, typically alkyl or benzyl groups of 1 to 7 carbon atoms. The compounds are useful in dental compositions because of their specific antiplaque activity. Examples include dodecyltrimethylammonium bromide, benzyldimethylstearylammonium chloride, cetylpyridinium chloride and quaternized 5-amino-1,3-bis(2-ethylhexyl)-5-methyl hexahydropyrimidine.
U.S. Pat. No. 4,370,314 broadly suggests that polymeric cationic quaternary antibacterial agents are also useful. However, no specific polymer examples are disclosed. Experimental evidence has shown that many polymerized cationic quaternary compounds are ineffective as antibacterial agents or less effective than the monomers from which they are derived. Many of the polymers are not water-dispersible. That is they are either insoluble or incapable of forming stable suspensions in aqueous media. Good coating coverage of the polymers onto substrates such as human teeth cannot be obtained. Without good coatings, the antibacterial activity of such polymers will be spotty.